Rechargeable lead-acid batteries have become the standard energy source used for starting motor vehicles and powering various electrical loads on the vehicle. If this battery is allowed to be discharged to a very low state-of-charge (SOC), the operator may be unable to start the vehicle engine. The problem is exacerbated when a high current load such as an electric winch is operated, whether or not the vehicle engine is running. Repeated, deep discharging a battery will also reduce the number of charge/discharge cycles the battery can perform and may even permanently damage the battery. Many efforts have been made to avoid over discharge of a vehicle battery and examples are commonly assigned U.S. Pat. No. 3,395,288 (Von Brimer), U.S. Pat. No. 3,646,354 (Von Brimer), U.S. Pat. No. 4,039,903 (Russell), U.S. Pat. No. 4,080,560 (Abert), U.S. Pat. No. 4,493,001 (Sheldrake), U.S. Pat. No. 4,902,956 (Sloan), U.S. Pat. No. 5,089,762 (Sloan), U.S. Pat. No. 5,136,230 (Gayler), U.S. Pat. No. 5,140,250 (Morland), U.S. Pat. No. 5,200,877 (Betton, et al.), U.S. Pat. No. 5,272,380 (Clokie), U.S. Pat. No. 5,321,389 (Meister), U.S. Pat. No. 6,037,749 (Parsonage), U.S. Pat. No. 6,242,891(Parsonage), U.S. Pat. No. 7,262,947 (Heravi, et al.), U.S. Pat. No. 7,791,310 (Luz, et al.) and U.S. Pat. No. 7,898,219 (Felps). The invention disclosed in U.S. Pat. No. 7,898,219 by Felps has proven itself to perform well in “real world” applications and is the basis for the present disclosure.
The need for a smart winch controller becomes apparent when one experienced in the art realizes an electric winch can draw up to hundreds of amperes (A) of current, which can quickly drain a battery. Even with the vehicle engine is running, the alternator will seldom be able to deliver sufficient current to maintain the battery's charge. This is especially true in small off-road vehicles such as all-terrain-vehicles (ATVs), utility-task-vehicles (UTVs) and extreme-terrain-vehicles (XTVs) that typically have small batteries with low ampere-hour (AH) ratings (generally ranging from 15 to 45 AH) and low output alternators (generally 40 A and sometimes much less). This is not as much of a problem on larger vehicles such as sport-utility-vehicles (SUVs), large 4-wheel drive pickups and trucks that have high output alternators. But even then, some of these vehicles have electric winches with much higher pull ratings; and therefore, much higher winch current requirements. Another problem is at the high load currents winches can draw, the AH rating of the battery is significantly reduced (as much as 35% or more) because of the Peukert effect (a measure of how well a battery holds up under heavy loads). An ATV/UTV/XTV winch rated at 4500 to 5000 pounds (lbs.) can draw as much as 330 A of current. The SOC on a 28 AH battery delivering 85 A of current can drop by more than 19% in 2.5 minutes. So care must be exercised to preserve the battery's SOC when a winch is being operated. Battery choice for off-road vehicles is very important because their environment can be extreme and those equipped with an electric winch place special demands on the battery. An absorbed-glass-matt (AGM), lead-acid battery is best since it is more rugged than a flooded, lead-acid battery. The Odyssey line of AGM batteries seem to be in a “league all their own” since their batteries can be purchased with a metal casing (for high heat applications), have extreme vibration resistance, have a higher energy density than spiral wound batteries and are certified as “dry cell” (for shipping and mounting purposes).
A second reason for needing a smart winch controller is that winch manufacturers generally design vehicle electric winches for intermittent use. The reason for this is to keep the size, weight and cost to a minimum. But, continuous use of these winches will result in overheating of the motor windings, synthetic rope, relays, wiring and wiring connections. A difficulty in solving that problem is that winch manufacturers are inconsistent about rating the cycle times of their winches. Most adhere to a 15 minute cycle time, but some rate fixed off times that can be as little as 10 minutes. The off time is to allow the winch time to cool down. Most specify a maximum on time of 2.5 minutes for any level of winch current and a maximum on time of 10 to 45 seconds at the maximum rated winch current. The specifications for winches include the maximum pull rating in lbs. for the first layer of wire rope on the winch drum and the maximum current the winch requires for pulling that weight. This maximum current rating can be used for controlling the winch. In practice, few operators use their winches when they are unwound to the first layer and they might be pulling on something that won't move (e.g. removing a tree stump). And, under these conditions, it is easy to overload the winch (i.e. sudden excessive current).
Various attempts have been made to prevent damage to an electric winch. Some examples of these winch controllers are: U.S. Pat. No. 4,873,474 (Johnson) and U.S. Pat. No. 6,046,893 (Heravi), all having some form of current limiting; U.S. Pat. No. 5,214,359 (Herndon, et al.), having current limiting and thermal protection (in the relay module used for winch direction); U.S. Pat. No. 8,076,885 (Heravi, et al.), having current limiting and under voltage protection; and, U.S. Pat. No. 6,864,650 (Heravi, et al.) and U.S. Pat. No. 8,213,137 (Fregoso), both being much more complex and having current limiting, under voltage protection, over temperature protection as well as other protection features. U.S. Pat. No. 5,648,887 (Herndon, et al.) has a complex current limit protection feature that takes into account multiple states of winch operation (including detecting the battery voltage) to adjust the current limit feature. Herndon addresses excessive energy delivered to a winch but fails to address the time required for the winch to cool down after normal winch use. All of these inventions provide different methods and levels of protection for the winch system and a controller to perform these functions, but all fail to address the maximum duty cycle rating of the winch, the minimum cycle time and the SOC of the battery. The patents that do monitor the battery voltage (except U.S. Pat. No. 5,648,887), have a single, minimum voltage limit that is not compensated for the internal resistance of the battery. In U.S. Pat. No. 8,213,137, Fregoso mentions “current vs time readings” in both his ABSTRACT and DETAILED DESCRIPTION OF THE INVENTION, but makes no CLAIMS about the phrase. Certainly it is advantageous not to damage the winch system, but either a dead battery or a damaged winch system has the potential of stranding an operator in a remote area.